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View Full Version : Many Levels Corrections

EpheMeroN
7th July 2005, 05:53
Before everyone tells me to learn how to do this myself, I'm in need of help mainly because my monitor's colors, brights, and darks are VERY screwed up. The monitor is 8 years old and I just don't have enough $$ for a new one yet. So any help on correcting the levels from these following clips is beyond appreciated :-)

CLIP #1
http://img149.imageshack.us/img149/3892/hsbooty1ta.th.jpg (http://img149.imageshack.us/my.php?image=hsbooty1ta.jpg)

CLIP #2
http://img149.imageshack.us/img149/5479/litakod016xb.th.jpg (http://img149.imageshack.us/my.php?image=litakod016xb.jpg) http://img149.imageshack.us/img149/3928/litakod021en.th.jpg (http://img149.imageshack.us/my.php?image=litakod021en.jpg)

CLIP #3
http://img160.imageshack.us/img160/817/noname80016mk.th.jpg (http://img160.imageshack.us/my.php?image=noname80016mk.jpg) http://img160.imageshack.us/img160/7304/noname80020fr.th.jpg (http://img160.imageshack.us/my.php?image=noname80020fr.jpg)

CLIP #4
http://img121.imageshack.us/img121/5651/noname944ur.th.jpg (http://img121.imageshack.us/my.php?image=noname944ur.jpg)

CLIP #5
http://img121.imageshack.us/img121/2206/wweraw018kg.th.jpg (http://img121.imageshack.us/my.php?image=wweraw018kg.jpg) http://img121.imageshack.us/img121/6996/wweraw028pr.th.jpg (http://img121.imageshack.us/my.php?image=wweraw028pr.jpg)
Mug Funky
7th July 2005, 06:08
they're all pretty good except for black point. you can do this without having a decent monitor using the levels in virtualdub - just line the input black level (the upper left arrow) with the beginning of the tall spike on the left side of the graph and you'll have the correct black point - type the values into avisynth's levels and you're set.

btw, i just got a spiffy 19" trinitron for AUD $150 the other day (USD $110) - 2nd-hand is the way to go for this stuff (so long as you can test the monitor before you buy it :)).
EpheMeroN
25th July 2005, 03:48
Okay, I just did that on one of the videos. I also changed the bottom bar's numbers as well from 0-255 to 16-235 because this will be for DVD and meant to be watched on a TV. How do I import these numbers into The AviSynth Levels Filter?

Below is a screencap of the levels adjustment I just did in Vdub:
http://img333.imageshack.us/img333/1091/untitled6fv.jpg
Mug Funky
25th July 2005, 06:04
simple - go into "configure" mode (so it gives you real values, not rescaled to 0-1.0 values) and type the values into avisynth this way:

levels(in_low,gamma,in_high,out_low,out_high)

you wont need to clamp ranges because you're working in yv12 and they should already be pretty much right. also levels has a coring capability built in (disable with "coring=false" in the levels command).
EpheMeroN
25th July 2005, 07:58
So just to verify, a correct levels filter entry based on my example would look like this? Levels(52,1,255,16,235)
mg262
25th July 2005, 08:29
In your example screenshot, the levels command maps 1.00 to 1.00... i.e. seems to preserve 255. Could you doublecheck that you actually entered 235 as the upper output range when you generated that screenshot?
EpheMeroN
27th July 2005, 20:55
In your example screenshot, the levels command maps 1.00 to 1.00... i.e. seems to preserve 255. Could you doublecheck that you actually entered 235 as the upper output range when you generated that screenshot?
Sorry for the confusion. I actually did leave the upper output range at 255 when I did that screenshot. But when I tried it again, I entered 16-235 as the lower and upper output ranges simply because this video will be encoded to MPEG-2 and burnt to dvd. With saying that, is it better to leave the levels at their default and use ColorYUV(Levels="PC->TV") or Limiter() instead? I have no idea if there's a difference, or if all 3 commands will do the same thing.
Wilbert
31st July 2005, 12:39
@EpheMeroN,
So just to verify, a correct levels filter entry based on my example would look like this? Levels(52,1,255,16,235)
Be aware that VDub uses RGB values. You can use the same ones in AviSynth IF your clip is RGB.

If your clip is YUV, Levels(52,1,255,16,235), does the following:

1) clamps input to [16,235]. So 0-16 is rounded to 16 and 235-255 to 235. (This is always done for a YUV clip! A RGB clip is not clamped.)

2) scales (after the clamping in (1)) [52,255] to [16,235].

ex1) Y=255 is rounded to Y=235, which is scaled to Y=235.
ex2) Y=200 is scaled to: 255->235 => 200->200*235/255=184.

btw,

limiter() just clamps, and ColorYUV(Levels="PC->TV") scales. I take it you know the difference between those.

I hope it's a bit clear.